FUNDAMENTALS OF AGRICULTURE. 



COW PEAS IN ROWS: A GOOD METHOD OF MAINTAINING SOIL FERTILITY. 



during any single season of growth, but a small amount 

 is absorbed directly from the mineral base of the soil 

 and added to the revolving fund after going through 

 the crop. The diagram also illustrates the ways in 

 which this revolving fund is lost by erosion, by de- 

 composition of the organic matter, the carbon dioxide 

 passing off into the atmosphere; by the loss of material 

 in grain and vegetables sold on the one hand and of 

 animal products on the other. It also indicates the 

 loss of fertility by the leaching of manure. Another 

 source of gain is from the atmospheric nitrogen, which 

 is absorbed by certain bacteria forming nodules on 

 members of the legume or pea family of plants. A 

 study of this diagram will show the great complexity 

 of the problem of maintaining the fertility of the soil. 

 It is possible to estimate the losses in some of the ways 

 indicated, as, for instance, in the products sold from 

 the farm and to a certain extent from the manure, but 

 the losses by leaching and by erosion as well as by de- 

 composition of organic matter, it is almost impossible 



